1. Field of Invention
This invention relates to an integrated circuit (IC) fabricating process, and more particularly relates to a method of patterning a hard mask layer for defining a deep trench.
2. Description of Related Art
In the IC technology, there are many cases where a device is formed in a deep trench in the substrate to save the circuit area. For example, the capacitors of the memory cells of embedded DRAM can be formed in deep trenches in a substrate.
The deep trenches are usually defined by a hard mask layer for having a large depth. The hard mask layer usually includes silicon nitride (SiN), which can be etched by an etching gas containing fluorohydrocarbons, such as CHF3 and CH2F2. However, when such etching gas is used, the chamber wall has a severe polymer deposition issue so that the chamber has to be maintained frequently.